1. Field of the Invention
The present invention relates to a memory control unit for a computer for processing two-dimensional image data, and more particularly to a memory control unit used to extract only a necessary portion of two-dimensional image scan data at a high speed to store it in continuous or discontinuous areas of a memory unit and synthesize partial image data stored in the memory unit at a predetermined portion of a two-dimensional image data.
2. Description of Prior Art
It has been known to scan document data of references or documents by a facsimile to write the data into a memory of a computer. A process for selecting only data relating to a partial image from the document image data written into the memory and transferring it to another memory area is called a partial image extraction. As shown in FIG. 1, partial image data 2 in a hatched area of two-dimensional image data 1 stored in the memory is extracted and loaded into continuous areas of a memory. The opposite process is called synthesis.
The extraction/synthesis process of the two-dimensional image data has heretofore been carried out by software which involves a long processing time. Assuming that the resolution of the scan lines of the facsmile is eight lines/mm, the overhead per data transfer is one millisecond and a data transfer rate is one megabyte/second, it usually takes five seconds or more to extract 60 blocks of a partial image data of 1 cm.times.10 cm area.